1. Technical Field
The present invention relates to devices and methods for use in spine surgery. In particular, the present invention relates to prosthetic devices that can implanted in the annulus fibrosis of a intervertebral disc for purpose of occluding defects in the annulus fibrosis so as to impede further loss of nucleus pulposus through such defects. The present invention also relates to instrumentation associated with implanting such annular repair devices.
2. Background Art
The human spine is comprised of thirty-three vertebrae at birth and twenty-four as a mature adult. Between each pair of vertebrae is an intervertebral disc, which maintains the space between adjacent vertebrae and acts as a cushion under compressive, bending and rotational loads and motions. The intervertebral disc contains three major components: a nucleus pulposus (a fluid-like component comprising proteoglycans and collagen), an annulus fibrosis (a flexible, collagen-based ring surrounding the nucleus pulposus) and a pair of cartilaginous endplates which help enclose the nucleus pulposus within the annulus fibrosis. A normal, healthy nucleus pulposus acts much like a pressurized fluid by transferring and distributing compressive load to the annulus fibrosis, thereby causing a slight expansion of the annulus fibrosis. However, injury and/or degeneration of the intervertebral disc in the human spine can be caused by disc herniation, rupture of the annulus, prolapse of the nucleus pulposus, mechanical instability of the disc and/or dehydration of the disc, thereby leading to neck and back pain, pain in the extremities, numbness and weakness. In addition, damage or degeneration of the annulus fibrosis in the form of a herniation, tear and/or crack reduces its ability to resist the tensile stresses conferred by the nucleus pulposus. Thus, the disc experiences excessive bulging that may result in spinal cord and/or nerve root impingement and subsequent pain, numbness, and weakness. Further, the nucleus pulposus can herniate into the foramenal spaces, causing irritation of nerve roots and foramenal stenosis.
Treatments such as discectomy, laminectomy, laminotomy and/or spine fusion procedures represent state of the art surgical treatment for disc problems. Typically, the goal of these treatments is to relieve pressure on the neural elements by eliminating the material causing stenosis or irritation of the neural elements. However, discectomy when performed alone can result in significant loss of disc height and frequently provides only temporary pain relief. Laminectomy/laminotomy procedures also provide only temporary relief by opening up the spinal canal and decompressing the neural elements, which is susceptible to restenosis due to scar tissue formation at the operative site. Spine fusion is considered by some to be a last resort, “most” invasive procedure that eliminates the flexibility of the motion segment and usually involves permanent hardware implantation. Furthermore, fusing spinal segments has been linked to adjacent level disc degeneration. All of these techniques have the disadvantage that they require extremely invasive surgical intervention to carry out the treatment.
There is, therefore, a need for a device and an improved method for excising and repairing disc herneations in a simple less invasive manner that can seal the annulus fibrosis and prevent subsequent expulsion of nucleus pulposus from the repaired disc.